JPH0387907A - Reference current source circuit containing lsi - Google Patents

Abstract

PURPOSE:To obtain an output constant current having high accuracy and high temperature characteristic by setting a constant current having no temperature coefficient or a corrected constant current with trimming by means of an element contained in an LSI and furthermore trimming the variance of a time constant against the current absolute value or the built-in capacity. CONSTITUTION:A temperature characteristic compensating voltage trimming circuit 1 applies a constant current I1 to a constant voltage diode ZD, divides the constant voltage VZ into VSU, VBC and VBD with the voltage dividing resistances RU, r1, r2 and RD respectively, and selects one of these divided voltages via a VB selection switch SW to supply it to a common base B of npn transistors TR Q1 - Q3. The resistance voltage (VB - VBE) obtained by subtracting the base-emitter voltage VBE from the reference voltage VB is applied to the emitter resistances R1 - R3 respectively. Then the current I1 - I3 obtained by dividing those emitter resistances by each resistance value are outputted from the collectors of the TR Q1 - Q3 respectively. Thus an output constant current I0 which is selectively synthesized with grant of duplication via the current switches S1 - S3 is obtained through an output terminal T0. In such a constitution, an output current having high accuracy is obtained.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an LSI built-in reference current source circuit.

[Conventional technology]

With the high precision of characteristics required of recent LSIs.

Product variations in temperature characteristics and characteristic values of reference current source circuits built into LSIs are becoming increasingly problematic.

Conventionally, when incorporating a reference current source circuit inside an LSI, a relatively stable reference voltage source such as a Zener diode or bandgap reference was created, and a reference current obtained by dividing this by a resistor was used. There is.

When this resistor is built into an LSI, the stability of the reference current is not good due to variations in absolute accuracy and temperature coefficient.

In order to obtain a highly accurate constant current, international
INTERNATIONAL C0N-FEREN
CE ON CONC0N5U ELECTRONIC
3), Digest on Technical Papers (IMGEST○F TECHNICAL PAPER)
3), 1989, p. 151, uses a highly accurate and highly stable external reference resistor.

For example, the absolute accuracy of the reference resistance is ±20%, and the temperature coefficient is 20%.
00PPM/'C, and the operating temperature range is (-25 to +2
5 to +125)°C, the error in resistance value is at most -3
It becomes 0 to +40%. Also, if you configure a capacitor charging circuit using a constant current source with such a large error,
The time constant is also about -30 to +40%.

[Problem to be solved by the invention]

The above-mentioned conventional LSI built-in reference current source circuit has the disadvantage that a highly stable and highly accurate reference resistor must be externally attached in order to obtain good temperature characteristics.

An object of the present invention is to provide a highly stable LSI built-in reference current source circuit that does not require an external high-performance reference resistor.

[Means to solve the problem]

The LSI built-in reference current source circuit of the present invention includes a temperature characteristic compensation voltage trimming circuit that trims a divided voltage value of an internal constant voltage and outputs a reference voltage, and an emitter (source) that inputs the divided voltage value to a common control terminal. a plurality of transistors each having a current setting resistor, one end connected to the collector (drain) of the transistor and the other end supplying an output current to a common output terminal, and a plurality of current switches that output a trimming setting signal and output the reference voltage. and a trimming setting circuit having a one-time write memory means for performing trimming of the current switch and trimming setting of the current switch.

Further, the LSI built-in reference current source circuit of the present invention includes a voltage trimming circuit for temperature characteristic compensation having a band gap type reference voltage source that outputs a predetermined reference voltage, and a temperature characteristic compensation voltage trimming circuit that inputs the reference voltage to one end and returns it to the other end. An operational amplifier that feeds back voltage and the output signal of the operational amplifier are input to the control terminal, the emitter (source) is connected to a trimmable current setting resistor to generate the feedback voltage, and the collector (drain) is connected to the output terminal for output regulation. The trimming setting circuit includes a constant current trimming circuit that supplies a current, and a trimming setting circuit that has a one-time write memory means that outputs a trimming setting signal and performs trimming of the reference voltage and trimming setting of the current switch. .

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of a first embodiment of the present invention.

The reference current source circuit generates a reference voltage v! which is proportional to the constant voltage v2.
Select the temperature characteristics compensation voltage trimming circuit 1 having 3 select switches S, the common base B inputs the reference voltage V, and each emitter inputs the current setting resistor R.
1 to R1, each collector is a current switch S
, ~S, to a common output terminal T0.

EPROM in which trimming information is set in the LSI manufacturing process by a constant current trimming circuit 2 having a constant current trimming circuit 2 and a write circuit 6.
5 and its output signal, a drive signal d is sent to the select switch S 8, and a drive signal d is sent to the current switches S1 to S.
1 to d, and a trimming setting circuit 3 having a register 4 that supplies signals 1 to d, the low resistance rl*r2 of the configuration is set to a value of about 10%.

Therefore, the upper and lower divided voltages V,..., Vゎ are the center divided voltages'! !
They are set to +10% and -10%, respectively, with respect to IEEvBc.

There is.

Therefore, the deflector currents and currents of transistors Q 2 and Q 3 are respectively 0. IL and o
, 2L.

Next, the operation of the circuit will be explained.

The temperature characteristic compensation voltage trimming circuit 1 applies a constant current to a constant voltage diode ZD, and applies a constant voltage v2 to a voltage dividing resistor R.
, j, r l+ r 21 Ra and V
The voltage is divided into 8°+VBD, one of which is selected by the VB select switch SW, and supplied to the common base B of the NPN transistors Q, ~Q.

The resistance voltage (V yaw V y o.) obtained by subtracting the base-emitter voltage V □ from this reference voltage ■8 is the value of each emitter resistance R1 to R
1 and divided by the respective resistance values, the currents, ~, are output from the collectors of the transistors Q1 to Q, and are selectively switched using the current switches Sl''Ss to allow overlap. The output constant current I0 is obtained from the output terminal T.

Here, if the temperature characteristic of the voltage v2 of the constant voltage diode ZD of the voltage trimming circuit 1 for temperature characteristic compensation is O, the divided reference voltage 3 has no temperature characteristic, and the position selection of the VB select switch Sw is Therefore, the reference voltage VB becomes VB
! It only changes to + * V BCr V BD.

For example, the collector current of transistor Q+ in constant current trimming circuit 2 is generally expressed by equation (1).

I+=(VB VIE)/R1-" (1) When this is differentiated logarithmically with respect to temperature T, the equation (2) is obtained.

...... (2) (+2000ppm) /℃, (VBVBri
It becomes 0.

Conversely, it can be seen from equation (2) that by changing the value of VB, the output current can be given a more or less positive or negative temperature characteristic.

Conversely, by slightly changing the reference voltage v8, it is possible to trim variations in the primary temperature characteristics of each resistor and the base-emitter voltage VBp.

As mentioned above, set the VB select switch SW to the center voltage MBC in advance and set the output constant current. The output current is designed so that the temperature characteristics of For example, in the case of a temperature coefficient of 10, trimming information is written in the EPROM 5 of the trimming setting circuit 3 to select the larger voltage VIlU, and the trimming signal d is output from the register 4.

Now, regarding the transistor current generator, as mentioned above, a constant current source with no temperature characteristics was obtained as the output current I0, but
Furthermore, to set the constant current value of this current source, the reference voltage ■3
It is necessary to perform trimming based on the variation ΔR of the current setting resistor R1.

Therefore, using R2 and Ri, which have the same temperature characteristics as R1, transistor Q2. Transistor current in Q3, 'Is
When obtained, these currents also have the same temperature characteristics as the collector current 11.

Also, since the manufacturing process is the same, the transistor current Ill I
It is relatively easy to determine the relative ratio between 2 and .

Here, if you set the transistor current, ~, as described above, you will get the output constant current. As I+, 1. IL, 1.
2L 1.3L are current switches Sl to S.

Therefore, by making I1 slightly smaller than the predetermined output current value I0 in advance and selecting one of the above, ±0.05I can be obtained. The width can be trimmed.

To set the combination of current switches 81 to S, in order to trim the reference current source circuit during the manufacturing process, first temporarily select only the center divided voltage vB0 and current switch Sl with the v3 select switch Sw, and then set the output. Current■. Find the first-order temperature coefficient of Combination trimming signal d1~
d.

Write settings in the one-time EPROM 5 so that it can be output.

Hi In this case, the memory may be a 4-unit ROM.

Furthermore, the number of resistors, transistors, and switches may be increased in order to perform fine trimming.

The transistor may be a MOS type.

FIG. 2 is a circuit diagram of a second embodiment of the invention.

A bandgap reference type circuit is used as the constant voltage circuit, and the transistor Q12 is replaced by a diode Q.
The junction size is 10 times that of l+, and the diode current is
and the transistor current, □ can be obtained from equations (3) and (4), and =1.・exp(qVp/kT) −(
3) I 12= 10 I 5exp (q VB!!1
2/ k T) --(4) Here I++ and I+
2 are equal, diode voltage VD and transistor voltage VB! Between +2 and (5) (VD VB++u
) = −・Iln l tJ −−(b) In other words, this voltage difference means that a voltage with a positive temperature coefficient proportional to T is obtained across the emitter resistor R1, and this voltage is expressed as R12/R1
Make the temperature coefficient of the collector voltage of the transistor Q13 8 zero or any desired value by multiplying by I can do it.

Voltage trimming circuit for temperature characteristic compensation 1. By selectively connecting resistors R1, .

Incidentally, the diodes DI and D2 are a type of HIELZ ROM that can be destructively short-circuited by applying a current.

The collector of the transistor Q13 is the output voltage ■8 of this constant voltage circuit, and this voltage and the emitter voltage vI! of the transistor Q14 are the same. Feedback is applied to the operational amplifier A1 so that the values are equal.

Therefore, the current value is this voltage (■8) divided by the resistor RI6. flows through transistor Q14.

Capacitor C is this constant current converter. Short circuit switch by
Charging starts when , is turned off, and the voltage Vc across it is expressed by equation (6), where t is time.

The ratio of this voltage to the reference voltage (7) is inverted by the comparator A2.

That is, the delay time t of the delay circuit 7 is 1.
- It is shown in equation (7).

Here, as mentioned above, the reference voltage (8) can have a desired temperature coefficient, so by making the temperature characteristics of this and R+s equal, the current VR/R1 of the transistor Q14
A temperature coefficient of 6 can be compensated for.

Furthermore, if we use a voltage source with a comparison voltage ■, which has no temperature coefficient as V, and ignore the temperature coefficient of capacitor C, since the temperature coefficient of a capacitor inside an LSI is usually small, the delay time t does not depend on the temperature. It can be kept constant.

Of course, the temperature characteristics of the comparison voltage (2) and the voltage V can be determined so as to strictly correct the temperature coefficient of the capacitor C.

In this case, the variation Δt in the delay time t is mainly C
” Since it is determined by the variation in R+s, the value of resistor R16 is trimmed according to the variation ΔC in capacitor C.
By setting the product to a predetermined value, the variation Δt in the delay time t can be eliminated.

Current resistors R+r to R19 and diodes D3 to D are trimming circuits for this purpose.

This embodiment differs from the first embodiment in that the value of the current source with the temperature coefficient corrected is set so as to correct the variation ΔC of the built-in capacitor C.

In addition to the delay circuit 7, this example can be applied to circuits that determine the time constant of one-shot multipliers, oscillators, filters, etc., and it is possible to create a time constant that has no temperature characteristics and has little variation.

The present invention is not limited to FIG. 1 and FIG. 2, and may employ a suitable combination of the two, various reference voltage circuits, memory means, or current synthesis means.

〔Effect of the invention〕

As described above, according to the present invention, a constant current with no or corrected temperature coefficient is set by trimming using elements inside the LSI, and variations in the absolute value of the current or the time constant with the built-in capacitance are also trimmed. As a result, a reference current source circuit having a constant output current with good accuracy and temperature characteristics can be obtained.

This means that it is possible to create high-precision current output and time constants without attaching high-performance external resistors to the LSI, and the terminals that were conventionally attached externally to obtain high precision can be used for other functions. In addition to making it possible to improve the degree of integration and eliminating the need for high-precision external resistors, this has a great industrial effect.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a first embodiment of the invention, and FIG. 2 is a circuit diagram of a second embodiment of the invention. 1.11...Voltage trimming circuit for temperature characteristic compensation, 2,2.・・・・・・Constant current trimming circuit, 3,3
．． ...Trimming setting circuit, 4...Register, 5...EPROM, 6...Writing circuit, 7...Delay circuit, d, d+~d,
...Trimming setting signal, ■, ...Constant current, engineering.・・・・・・Output constant current, Q1~Q1...
...Transistor, R1-R1...Current setting resistor, Rv, Ro...Voltage dividing resistor, S1-S,...
...Current switch% Sl...VB□Select switch, To. 'ro1...Output terminal, V, VR...
Reference voltage, V2... Constant voltage.

Claims (2)

[Claims] (1) A temperature characteristic compensation voltage trimming circuit that trims the divided voltage value of the internal constant voltage and outputs a reference voltage, and a plurality of voltage trimming circuits that input the divided voltage value to a common control terminal and have a current setting resistor at the emitter (source). a plurality of current switches, one end of which is connected to the transistor and the collector (drain) of the transistor, and the other end of which supplies an output current to a common output terminal; and trimming of the reference voltage and trimming of the current switch by outputting a trimming setting signal. 1. A reference current source circuit built into an LSI, comprising a trimming setting circuit having a one-time write memory means for performing setting. (2) a temperature characteristic compensation voltage trimming circuit having a bandgap reference voltage source that outputs a predetermined reference voltage;
An operational amplifier that inputs the reference voltage at one end and feeds back a feedback voltage at the other end, and an output signal of the operational amplifier is input to the control end, and the emitter (source) is connected to a trimmable current setting resistor to generate the feedback voltage. a constant current trimming circuit whose collector (drain) supplies an output constant current to an output terminal, and a one-time write memory means which outputs a trimming setting signal to trim the reference voltage and set the trimming of the current switch. An LSI built-in reference current source circuit comprising: a trimming setting circuit having a trimming setting circuit;